Here you go http://jsfiddle.net/Ka89Q/4/
var head = [],
i = 0,
tableObj = {myrows: []};
$.each($("#my_table thead th"), function() {
head[i++] = $(this).text();
});
$.each($("#my_table tbody tr"), function() {
var $row = $(this),
rowObj = {};
i = 0;
$.each($("td", $row), function() {
var $col = $(this);
rowObj[head[i]] = $col.text();
i++;
})
tableObj.myrows.push(rowObj);
});
alert(JSON.stringify(tableObj));